Gwyneth's good pal Beyonce arrived fashionably late but her husband Jay-Z was not spotted suggesting he stayed home with their baby Blue Ivy.

Gwyneth arrived at the party with her new best friend 'What to Expect When You're Expecting' star Cameron Diaz, who also celebrated turning 40 in August.

The blonde actresses got ready for the party together and both had their hair done by top stylist Josue Perez, according to insiders.

A source told USMagazine.com: "They are really fun and close. They were having a great time getting ready for the party. There were lots of laughs."

Earlier this week Gwyneth said she was terrified about turning 40.The actress - who has two children Apple, eight and six-year-old Moses with husband Chris Martin, 35 - admitted she was not looking forward to reaching the milestone age on September 27 but now that her birthday is over she feels "happy and content".

She said: "I was really worried about it, leading up to the day, but now I feel really happy and content with my life. I'm excited to move into the next phase. It's much more exciting than I thought it would be.

"I think I try to promote self-growth and reflection for myself every day."